Add test "TestInterpolatedStringWithNewLinesInExpression()" which was…

… implemented as part of dotnet#50799 and later realized via dotnet#56853

src/Compilers/CSharp/Test/Syntax/Parsing/ExpressionParsingTests.cs

@@ -207,6 +207,33 @@ void M()
             EOF();
         }
 
+        [Fact]
+        public void TestInterpolatedStringWithNewLinesInExpression()
+        {
+            var text = @"$""Text with {\nnew[] {\n 1, 2, 3 \n}[2]\n}parts and new line expressions!""";
+            text = text.Replace(@"\n", System.Environment.NewLine);
+
+            var expr = this.ParseExpression(text);
+
+            if (expr is InterpolatedStringExpressionSyntax intStr)
+            {
+                Assert.Equal(3, intStr.Contents.Count);
+
+                Assert.IsType<InterpolatedStringTextSyntax>(intStr.Contents[0]);
+                Assert.IsType<InterpolationSyntax>(intStr.Contents[1]);
+                Assert.IsType<InterpolatedStringTextSyntax>(intStr.Contents[0]);
+
+                Assert.Equal("Text with ", intStr.Contents[0].ToString());
+                Assert.Equal("parts and new line expressions!", intStr.Contents[2].ToString());
+
+                Assert.IsType<ElementAccessExpressionSyntax>(((InterpolationSyntax)intStr.Contents[1]).Expression);
+            }
+            else
+            {
+                Assert.True(false, "Invalid expression type returned");
+            }
+        }
+
         [Fact]
         public void TestName()
         {